Circa 2009, the Internet was in a stage of its evolution in which the backbone (routers and servers) was connected to fringe nodes formed primarily by personal computers. At that time, Kevin Ashton (among others) looked ahead to the next stage in the Internet's evolution, which he described as the Internet of Things (“IoT”). In his article, “That ‘Internet of Things’ Thing,” RFID Journal, Jul. 22, 2009, he describes the circa-2009-Internet as almost wholly dependent upon human interaction, i.e., he asserts that nearly all of the data then available on the internet was generated by data-capture/data-creation chains of events each of which included human interaction, e.g., typing, pressing a record button, taking a digital picture, or scanning a bar code. In the evolution of the Internet, such dependence upon human interaction as a link in each chain of data-capture and/or data-generation is a bottleneck. To deal with the bottleneck, Ashton suggested adapting internet-connected computers by providing them with data-capture and/or data-generation capability, thereby eliminating human interaction from a substantial portion of the data-capture/data-creation chains of events.
In the context of the IoT, a thing can be a natural or man-made object to which is assigned a unique ID/address and which is configured with the ability to capture and/or create data and transfer that data over a network. Relative to the IoT, a thing can be, e.g., a person with a heart monitor implant, a farm animal with a biochip transponder, an automobile that has built-in sensors to alert the driver when tire pressure is low, field operation devices that assist fire-fighters in search and rescue, personal biometric monitors woven into clothing that interact with thermostat systems and lighting systems to control HVAC and illumination conditions in a room continuously and imperceptibly, a refrigerator that is “aware” of its suitably tagged contents that can both plan a variety of menus from the food actually present therein and warn users of stale or spoiled food, etc.
In the post-2009 evolution of the Internet towards the IoT, a segment that has experienced major growth is that of small, inexpensive, networked processing devices, distributed at all scales throughout everyday life. Of those, many are configured for everyday/commonplace purposes. For the IoT, the fringe nodes will be comprised substantially of such small devices.
Within the small-device segment, the sub-segment that has the greatest growth potential is embedded, low-power, wireless devices. Examples of low-power, low-bandwidth wireless networks include those compliant with the IEEE 802.15.4 standard, the “Zigbee protocol,” the 6LoWPAN standard, the LoRaWAN standard (as standardized by the LoRa™ Alliance), etc. Such networks are described as comprising the Wireless Embedded Internet (“WET”), which is a subset of IoT.
Most of the WET operates in portions of the RF spectrum that are unlicensed by a government's regulatory authority. Examples of unlicensed spectrums include the industrial, scientific and medical (ISM) radio bands reserved internationally for the use of radio frequency (RF) energy for industrial, scientific and medical purposes other than telecommunications, e.g., as regulated in the U.S.A. by FCC Part 15, with such regulations including requirements/constraints on frequency hopping, etc. An example of a telecommunications technique used in the 915 MHz ISM band is the LoRa™ modulation format that is included in the LoRaWAN standard. The LoRa™ modulation format can be described as a frequency modulated (“FM”) chirp that is based on the generation of a stable chirp using a fractional-N (“fracN”) phase-locked loop (“PLL”). Core LoRa™ technology is described in U.S. Pat. No. 7,791,415, which is assigned to Semtech™ Corporation. It is noted that the LoRa™ modulation format does not itself describe system functionality above the physical layer, i.e., above the RF medium.
It was assumed that Moore's law would advance computing and communication capabilities so rapidly that soon any embedded device could implement IP protocols, even the embedded, low-power, wireless devices of the WET. Alas, this has not proven true for cheap, low-power microcontrollers and low-power wireless radio technologies. The vast majority of simple embedded devices still make use of 8-bit and 16-bit microcontrollers with very limited memory because they are low-power, small and cheap.
For operation in the unlicensed spectrum, there are two conventional hopping schemes. It is assumed that a maximum of Q channels can be used for uplink (transmission from an end node to a central node).
In the first conventional hopping scheme, there is no hopping synchronization between the central node and the end nodes. Accordingly, the first conventional hopping scheme can be described as a zero hopping-synchronization scheme. For the first conventional hopping scheme, because the central node does not know over which of the Q uplink channels the end nodes will transmit uplink messages, the central node must listen for a transmission on each of the Q uplink channels during each frame. Arrangements in which ‘all-channel listening’ has been implemented include: an all-physical arrangement in which the central node is provided with Q physical receivers so that the central node can listen concurrently on all Q uplink channels; and a partly-physical/partly-virtual arrangement in which the central node is provided with X physical receivers, where X is an integer and 1≦X≦Q. Under either arrangement, there is zero hopping synchronization,
Under the partly-physical/partly-virtual arrangement, the central node is provided with a buffer to record all transmissions (if any) with a given frame. Each of the X physical receivers is allotted a fraction Q/X of the Q uplink channels. For a given frame and for each of the X physical receivers, the following process is iterated over d where d is an integer and 0≦d≦(Q/X−1): a given physical receiver is tuned to one of the channels CH(d) in its allotment of Q/N uplink channels and then listens the corresponding recording for a transmission on CH(d). Under the case where where X=1, the allotment is Q/X=Q such that the iterative process is iterated Q times.
In the second conventional hopping scheme: it is further assumed that there are V end nodes, where V is an integer and 2≦V. Accordingly, for the second conventional hopping scheme, the central node is provided with V receivers because there are V end nodes such that there is one receiver for each end node. To ensure synchronization for the second hopping scheme, each of the V pairings of the central node with one of the V end nodes is provided with its own hopping plan, respectively, such that there are V distinct hopping plans. The second conventional hopping scheme can be described as a complete hopping-synchronization scheme.